Mud runs are considered by running enthusiasts to be a great physical and mental challenge. But here's why it's always best to know what you're getting into before signing up. A recent report from the Annals of Emergency Medicine has highlighted the hidden dangers that participants face when competing in mud runs.

The report focused on case studies involving 'Tough Mudder,' a popular 10- to 12-mile run which attracts a quarter-million participants to its races around the country. It also made headlines earlier this year after a 28-year-old participant reportedly died during the event.

The report reveals several startling injuries that participants suffered during an event held in Pennsylvania. While muscle injuries were also common, a startling 38 participants ended up being sent to the emergency room. Their injuries included electrical shocks to the head while running through water, burn marks and heart muscle inflammation from electrical injuries, partial paralysis, seizures, fainting, dehydration, and a dangerous condition linked to muscle breakdown called rhabdomyolysis.

The researchers also noted that some injuries suffered like paralysis were expected to be permanent. The authors noted that endurance training could help prevent problems like dehydration and rhabdomyolysis.